Biol 221 Lecture 5 MCQs

A major difference between Gram negative and Gram positive cell walls is:

• Gram negative walls have teichoic acid storage polymers

• Gram positive walls are made of peptidoglycan

• Gram negative walls are much thicker than Gram positive walls

• Gram positive walls are enclosed within a membrane-bound space

• Gram positive walls are crosslinked via a pentaglycine interbridge

The purpose of osmoprotectants accumulating within bacterial cells is to:

• prevent the cytoplasm from shriveling up in hyperosmotic environments

• prevent the cytoplasm from shriveling up in hypoosmotic environments

• prevent the cell from lysing in hyperosmotic environments

• prevent the cell from lysing in hypoosmotic environments

• Prevent the cell from either lysing or shriveling up, depending on the environment

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The PMF is used directly for all of the following EXCEPT:

• flagellar rotation

• transport through major facilitator (MFS) transporters

• transport of water through aquaporins

• ATP synthesis via chemiosmosis

• transport of the amino acid glutamate into the cell

In an environment that was isotonic to the cell’s cytoplasm, what effect would penicillin have on logarithmic phase Gram negative rod shaped cells?

• no effect

• The cells would lose their rod shape

• The cells would lyse but remain intact

• The cells would lyse

• The cells would become Gram positive

In this diagram of a Gram negative cell wall, which letter designates the O-antigen (O polysaccharide) component of the LPS layer?

• A

• B

• C

• D

• E

What would happen to Mycoplasma cells placed in a solution that was hypotonic with respect to the cytoplasm of the cells?

• They would plasmolyze

• They would synthesize osmoprotectants

• They would lyse

• They would experience an increase in turgor pressure, but would not lyse

• They would not experience any changes

Refer to the diagram peptidoglycan. What is different between Gram negative and Gram positive peptidoglycan?

• The structure marked "A" is only found in G+ cells

• The bond marked "B" is an α-1,4 bond in G+ cells and a β-1,4 bond in G- cells

• The amino acid marked "C" is an L-amino acid in G+ cells and a D-amino acid in G- cells

• The structure marked "D" does not exist in G- cells

• The molecule marked "E" is a sugar in G+ cells and an amino acid in G- cells

How does an amino acid get through the Gram negative outer membrane?

• By simple diffusion

• LPS is much more permeable than phospholipid

• By use of energy from the PMF

• Through special facilitated diffusion channels

• Through teichoic acid channels

What part of bacterial cells is called "endotoxin" because of its toxic effects in vertebrates?

• Peptidoglycan

• Flagella

• Pili

• Lipopolysaccharide

• Teichoic acids

Which of the following is NOT involved in the formation of a proton motive force (PMF) in bacteria?

• An electron transport chain

• An ion gradient across the cell membrane

• A charge separation (voltage gradient) across the cell membrane

• A proton pump that uses energy from sunlight

• An ABC transport protein

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